Battery management systems that rely on external cell performance parameters to determine state-of-charge (SOC) and/or state-of-health (SOH) result in conservative overdesign to manage the uncertainty in battery state-of-charge and battery degradation with aging. This reliance on conservative overdesign of batteries has affected the widespread adoption of clean technologies such as electric vehicles and power grid storage. Conservative overdesign of batteries arises in part because the battery state cannot be fully understood from external parameters alone.